Manufacture of bends from straight fiber tubes



Sept 27, 1932. M. o. Scl-lun E'r Al. 1999953 MANUFACTR OF BENDS FROM STRAIGHT FIBER TUBES Filed Agn-i1 so. 1930 envmar` Ptehtecl Sept. 27, 1932 UNITED STA MILTON o. scnun AND JOHN G. GossnLINKf, or BERLIN, NEW HAMPSHIRE, AssIGNoRs .fro BROWN COMPANY, or BERLIN, NnwIIAMPsIiInn, A coaronA'rIoN or MAINE MANUFACTURE or BENns Faoin: STRAIGHT IInna iruBns" Application led April 30,

This invention relates to the manufacture of bends from sraight fiber tubes, and more particularly `from tubes fA which .are made byV winding a wet web of interfelted cellulose bers on a mandrel into a wall of the desired tubes are removed from the mandrel in a wet,

plastic state, and are then thoroughly'dried. Heretofore, if bends were to be made from the tubes, they were dried or dewatered to a Vmoisture content at which they were rigidy to impart dielectric properties thereto.v Y

In a mill Where continuous large scale .pro-ik duction is being carried-out andthere is a progressive flow-of tubes through long dryers run on countercurrent principles, the ,foregoing practice of making bends presents some serious disadvantages. Thus, When'substam" tial quantities of tubes are withdrawn .from a dryer, the drying conditions, that is to say, the humidity and temperature conditions in the dryer, be seriously upset, as theremoval of large masses of wet pulp from a given section of the dryer interferes with the counter-current drying conditions in the dryer. TheV doors of the` dryer, wheniopened for the removal of the wet tubes, allow excesf sive leakage of fresh air into the dryer, accompanied by a disturbance in the equilibrium humidity conditions of the dryer. Again, if there is an order for asize of bend which is out of stock and which is not then being run on the machines, the operating schedule of the mill must be changed; and

1930. serial No. 448,550'.

a large excess of straight conduit which is at the time unnecessary must be made for the sake of a comparatively small proportionrof bends. vTt is almost impossible to forecast sufficiently closely the relative ,sales off straight and curved pieces to avoidthe, necessity for suddenlychanging the mill sched- `ule for the running of bends, even though there may be in stock an excessive quantity of straight impregnated conduit of the de-V sired diameter.-

Tt has been proposed,in the past, thatin order to prevent the upset of the dryer through the removal of partially dried tubes, the dry tubes bey remoistened to the,

necessary extent and then bent. This eX- pedient, however, necessitates thek storage of relatively large quantities of unimpregnated conduit, which is impracticable because conduit in this condition undergoes comparatively rapid weathering. VDuring-'storaga'it absorbs so much moisture that in the subsequent impregnations blisters are generated in the tube wall, as the moisture is expelled from the interior, unless the tubes are redried.

,The step of redrying, however, wouldl add materially: to the expense of manufacture.-

Further, these tubes, if piled to'. any material height, tend to become oval or -otherwise get out of shape.

In accordance with the present invention, straight fiber tubes are bent to the desired curvature after they have been impregnated, thereby not only eliminating the undesirable interference with the dryer which has here tofore been experienced, but also enabling the illing of orders for bends of any curvature -promptly,because of the customary practice to keep large inventories of impregnated straight fiber tubes. In order to effect the bending of impregnatedy tubes, it is necessary to effect their conversiouto a more or less soft and plastic condition. Vlhile various methods of softening and plasticization may be employed, it is mostpractical to bring about` this result by submersing the tubes in water until suflicient moisture has been absorbed thereby to render them plastic; Since l the impregnated tubes absorb water very slowly under ordinary conditions, the process may be hastened by exerting pressure upon the water, by raising the temperature, or by doing both. The hot water not only hastens the softening of the fibrous structure, rendering 5 it more or less limp, so that it may withstand bending stresses without undergoing rupture, but it softens the pitch or other thermoplastic material used as the waterproofing agent. If it were attempted to stretch a dry mat io of fibersbeyond a certain comparatively narrow range, tearing or breaking would result, but if the vfibrous Vmass is conditioned by moistening with water, the cellulosic bonding material in the form of gelatinized cellulose ley between the fibers apparently undergoes a 1 species of peptization, so'thatV when the' stretching forces are applied the fibers may slip relative to one another; and greater distortion of the mat ishence possible without quantities of Water. ln general,.water ab-` sorption of about 18% to 20% is desirable, which may be realized by treatin@ the pitch- Y impregnated tubes with water under, say, 35

form-maintaining springs may be inserted into the tubes and they may be bent to the desired curvature before losing their plasticity. If desired, however, the springs may be inserted into the tubes before they are sub-Q jected tothe action of water, in which case forms such as are customarily used 'for lpro-V not, however, hereinv claim a method whichcomprises inserting flexible form-maintaining devices into tubes, bending the tubes to the desired curvature, drying thebent tubes to a rigid condition, and finally removing the form-maintaining devices therefrom, as such a method is fully described in Letters Patent No. 1,602,165, issued October 5, 1926, to Howard Parker.

A preferred method of bending the tubesf which constitutes part of the present invention is with the. aid of curved springs, this method and the instrumentalities used therein `being illustrated on the accompanying drawing, wherein Figure 1 is a front view of a straight tube assembled with a normally curved, flat spring actuallytearing the mat. Inasmuch` as the.

pounds pressure per square inch for about eight hours at 298o F. Immediately afterv removing the tubes from the hot water bath,:

before the spring has exerted its bending action.

Figure 2 represents a section through the assembly on the line 2-2 of Figure 1.

Figure 3 is a view similar to Figure 1 but e@ showing the tube in bent condition. d f 4Figure 4 is a front view of only the spring member in its normal, curved condition.

Figure 5 represents a section through the spring on the line 5`-5 ofFigure 4.y g 75 Figure 6 is a view similar to Figure 1 but .illustrating the use of a normally curved helical spring as the bending means.

Figure 7 is a view similar to Figure 6 after the tube has been bent.

Figure 8 is a front View of only the'helical spring in its normally curved condition.

Referring in detail first to Figure 4 of the drawing, 1 indicatesa flat spring which normally has the vcontour which the inside edge.. of the bent tube is to assume. Y The spring" may be provided with suitable means for gripping the tube, for which purpose a plurality of spring clips 2 may be secured to the spring at suitably spaced intervals. For in?, stance, three clips may be used, one being at' the center and one near each end of the spring. Asbest shown in Figure 5., the clips are arcuate inform and a transverse section therethrougliconstitutes'an arc of substantially.-95 more than .1800, so that the edges 3 of the clips are separated a distance permitting the clipsto be sprung over and to embrace a tube while exerting sufficient spring action to maintain the straightened spring up kagainst-,100 the tubesubstantially throughout its lengthf" The assembly of the spring with a straight tube 3 is made by engaging the clips successively with'the straight tube, as a result of which the spring becomes straightened out, as`105 e vbends under the iniuence of the spring unti1110 the normal curvature of the axis of the spring is reached, as shown in Figure 3. The same result is, however, attainedif the tube is first rendered -plastic and the spring then assembled therewith. The clips serve a double .115 function, namely, that of gripping the tube and that of preventing it from undergoing bulging or other deformation Aas it yields.

z When a ynormally curved helical spring 5, such as shown in Figure 8, is usedin lieu of; 120 a flat spring, it should be of a diameter very nearly equal to the inside diameter of the tube, so Ythat when it is inserted in straightened out condition inside a tube 6 to effectbending of the tube, as shown inFigure 6, the circularity 125 of the tube will Vbe maintained as the tube lbends to. thenormal curvature of the spring,

bor to reduce its diameter so that it may be inserted in the tube, and then releasing it so that its convolutions Will eXpand against the inner Wall of the tube and exert the desired bending stresses on the tube. It is thus seen that by using properly shaped springs and assembling them with the straight tubes as described, the bending forces are automatically applied to the tube uniformly and steadily, andthe danger of rupturing the tubes by too rapid bending is avoided. The tubes yield gradually and uniformly to the bending forces at a rate Which is determined by their plasticity, so that too rapid bending, Which is accompanied by weakening of the fibrous structure, is avoided. n This latter objection may arise when a tube is bent by hand 'or by machinery, asin such case the rate of bending is not controlled by the plasticity of the tube, but depends upon the judgment and skill of the operator. The bending method of the present invention is especially advantageous in the bending of tubes impregnated With pitch or other thermoplastic materials, as in such case the plastic straight tubes are sulii' ciently strong to resist breakage or undesirable deformation by the tensioned, normally curved springs, and at the same time are suciently plastic to yield under the stresses eX- erted thereupon by the springs, and thus be brought to the normally curved condition of such springs.

The plastic tubes may be dried in their bent condition, and after they have been dried or set to a rigid condition, the springs may be removed therefrom and the tubes subjected to further treatment, if desired, such, for in- .tance, as coating with blown asphalt compositions of the type disclosed in Patent No. 1,71LifOQ, issued May 28, 1929, to Wallace B. Van Arsdel, or in patent application Serial No. 325,651, filed December 12, 1928, by Everett W. Lovering, or in Patent No. 1,751,935, issued March 25, 1930, to Everett W. Lovering and Vallace B. Van Arsdel.

rlhe principles of the present invention, While applicable With especial advantage in the manufacture of bends from pitch-impregnated ber tubes, may have application in changing the form or shape of other articles `Which have been impregnated With a thermoplastic Waterproofing material, such as pitch.

TWe claim:

1. A method of bending straight liber tubes While in a plastic state, Which comprises assembling such tubes With normally curved springs in straightened out condition, and permitting the springs to return to their normal curvature and to bend the tubes While they are in plastic state.

2. A method of bending a ber tube impregzjnated` With thermoplastic material While said tube is in a plastic state, which comprises engaging the tube with a normally curved spring to exert bending stresses thereon, and

In testimony whereof We have affixed our signatures.

MILTON O. SCHUR. JOHN Gr. GOSSELINK. 

